1. Field of the Invention
The invention relates to a toepiece of a binding device for securing a boot to a gliding board. This toepiece is particularly suitable for ski touring. It also relates to a binding device for securing a boot to a gliding board and to a gliding board as such equipped with such a binding device and/or such a toepiece.
2. Related Art
The document EP-A1-2353673 describes a toepiece of a binding device for securing a boot to a touring ski. The front binding of the boot is based on two jaws of the toepiece that are articulated about longitudinal pivot axes with respect to a base of the toepiece that is intended to be fixed to the touring ski. Each jaw comprises retaining elements that are intended to engage with the touring ski boot. The two jaws are articulated by way of a spring system in order to take up a first stable position, known as the closed position, in which the retaining elements engage with corresponding hollow parts formed laterally in the anterior part of the touring ski boot, in order to fix the boot, only allowing it to move in rotation about a transverse axis with respect to the ski, and a second stable position, known as the open position, in which the jaws are spaced apart such that the retaining elements free the boot, which can be separated from the touring ski. The front part of the boot is secured to a touring ski equipped with such a toepiece by positioning the boot such that the two jaws take up the second, open position, then by pressing strongly with the heel of the boot on the spring-based system, thereby allowing the articulated jaws to move towards their first, closed position in which they move towards the boot in order to position the retaining elements within complementary hollow parts of the boot.
A drawback with such existing toepieces is their lack of safety in the case of the skier falling, in particular in the case of a twisting fall on the part of the skier in a downhill situation of the alpine skiing type, involving a twisting movement of the boot with respect to the ski, during which the boot remains trapped in the toepiece, thereby risking injury to the skier.
A known manner for automatically freeing the touring boot in order to prevent injury to the skier is to provide a heel piece which is associated with such existing toepieces, is intended to fix the rear part of the touring boot and is configured so as to be able to free the boot in the event of a fall, in particular as a result of twisting, but also as a result of a forward fall and/or a backward fall. However, such heel pieces are complex, resulting in higher costs and substantial weight, and are unable to comply with safety criteria dictated by the alpine standard ISO9462. This limits the safety imparted to the touring skier.
The document EP-B1-1393783 describes another type of toepiece comprising jaws that are likewise articulated about longitudinal axes on a transversely mobile part. The jaws are in contact with a tilter which prevents the jaws from tilting while the movement travel of the mobile part is less than a given travel. Next, the jaws tilt and free the boot. However, this solution is complex, bulky and heavy on account of the existence of the tilter.
The document EP-A1-2431080 describes a toepiece having a fixed part and a mobile part that rotates about a vertical axis. The mobile part comprises two jaws that are conventionally connected by a knuckle joint mechanism having a lever, said jaws being integral with the mobile part. The lever selectively changes between a lowered position in which the toepiece is placed in an open position in which the jaws are spaced apart to allow the boot to be fitted in the toepiece, a semi-raised position in which the jaws are moved towards one another in order to place the toepiece in a closed position suitable for downhill use and a raised position in which locking elements that are integral with the lever are in contact with a cam surface that is integral with the fixed part in order to prevent any possibility of the lever returning towards the semi-raised position and towards the lowered position, thereby making it possible to prevent any releasing of the jaws and freezing the toepiece in a walking position. In the closed position of the toepiece, which is taken up in the semi-raised position of the lever, the mobile part can pivot over a predetermined limited angular travel, this pivoting taking place counter to the action of a return spring for returning the mobile part towards a centred position. In the walking position of the toepiece, which is taken up in the raised position of the lever, the lever is placed between lateral arms that are integral with the fixed part, thereby preventing the mobile part from pivoting with respect to the fixed part. In the event of a fall, in a first phase the heel is released in the region of the heel piece. This allows the entire boot to move. During this movement, the boot rotates the mobile part with respect to the fixed part until it comes into abutment at the end of its predetermined travel. This thus results in the mobile part suddenly stopping. In a second phase, the continuation of the movement of the boot on account of the fall, while the mobile part is in angular abutment, causes one of the jaws to be pushed, thereby causing the jaws to open and the lever to pass into its lowered position, freeing the boot. Thus, releasing takes place in two phases: in the first phase, during the rotation of the mobile part, the jaws are blocked in the closed position and retain the boot in the toepiece, whereas in the second phase, which starts when the mobile part comes into angular abutment, the jaws begin to open under the action of the boot and place the lever in the lowered position. However, this solution is again complex, bulky and heavy. The safety imparted is somewhat unsatisfactory, since releasing requires a very large angular movement of the boot.